Dr Lang said while that brought positives for workers and would potentially help the Cardiff economy, he questioned what it did for other local economies in south Wales.

To have real impact, his report said there needed to be more research into where people work, shop and access services like health care.

"We need to plan carefully where the infrastructure will be and its impact on local economies," he said.

Image caption
Studies have looked at how small businesses can be squeezed by hubs at urban metro systems like this one in Bilbao, Spain

"Will they support small local business or draw people out of communities?"

Up to £600m is being spent on the first phase of the Metro until 2020.

It is likely to be a mix of light rail, trams, improved trains and faster buses in Cardiff and the valleys. The eventual cost has been estimated at being between £2bn and £4bn.

Report findings

"Some ambiguity" over the location of Metro with Welsh Government refusing to commit to a map, the costs of the investment and timescales for completion

Criticism of a "lack of clarity" over how the Metro will be delivered and said ministers appeared "to bundle a range of transport projects together that claim to move the Metro forward"

The planned new £241m specialist critical care centre at Llanfrechfa Grange near Cwmbran was a "surprising omission" from the potential Metro map. It recommends a reappraisal of the map to ensure the Metro meets economic and social needs

Dr Lang's report casts a "critical friend's eye" over the proposals and highlighted that similar projects elsewhere in the world had not necessarily produced positive urban renewal and regeneration.

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Media captionDriverless pods were suggested to link the city centre and Cardiff Bay in 2002

He pointed to studies looking at similar projects in San Francisco and Bilbao, Spain, which found little direct impact on land use and potential negative effects on small businesses near transport hubs respectively.

Dr Lang urged more research into how towns and cities in the region are interconnected and said there was a "strong case" for a conversation with communities and local businesses about their priorities and to ensure consultation was not tokenistic.

FSB Wales policy unit chairwoman Janet Jones said: "Whilst there is broad support for the Metro project, important questions remain over what sort of economic impact the scheme will have."

She said the FSB was particularly concerned that any regeneration benefits from the project "must be felt not only at Cardiff but in communities across south east Wales that are served by the Metro network".